1. Field of the Invention
The present invention relates mainly to an absorbent article for absorbing and retaining a liquid waste such as menstrual blood and, more particularly, to an absorbent article having leakage preventing side walls on the two widthwise sides of the liquid receiving side.
2. Related Art
In the prior art, there have been a variety of absorbent articles including a sanitary napkin, a urine absorbing pad and a disposable diaper. These absorbent articles are demanded, when worn, for absorbing the liquid waste reliably in liquid absorbing layers so that the liquid waste may not leak to the outside of the absorbent articles. For this purpose, there is an absorbent article which is provided on the surface of the liquid receiving side with leakage preventing side walls extending longitudinally on the two widthwise sides.
In the general structure of the leakage preventing side walls of the prior art, a longitudinally extending unstretchable hydrophobic sheet is jointed to the top sheet of the absorbent article, and an elastic member extending longitudinally of the absorbent article is jointed to the hydrophobic sheet. By the elastic shrinking force in the longitudinal direction of the elastic member, a curving force in the longitudinal direction is applied to the absorbent article, and the leakage preventing side walls are raised to the liquid receiving side of the absorbent article so that the menstrual blood or the like may be prevented from leaking sideways.
In the leakage preventing side walls in which longitudinally extending elastic members are attached to the unstretchable hydrophobic sheet, however, this hydrophobic sheet is irregularly wrinkled by the longitudinal elastic shrinking forces of the elastic members. If the unstretchable hydrophobic sheet thus has many irregular wrinkles in which the ridges and valleys are individually extended in the widthwise direction and are repeated in the longitudinal direction, the leakage preventing side walls acquire a high bending rigidity in the widthwise direction so that they become planar in the widthwise direction. Then, the leakage preventing side walls hardly follow the shape of the skin surface of a wearer so that the wearer feels a sense of discomfort. If a high external force acts on the portion where the bending rigidity in the widthwise direction is high, moreover, the leakage preventing side walls are collapsed in the widthwise direction so that they remain broken to fail to restore their original shapes. As a result, the contact of the leakage preventing side walls with the wearer""s skin is easily deteriorated to cause a sideway leakage.
If the ridges and valleys of the irregular wrinkles are individually extended in the longitudinal direction and are repeated in the widthwise direction, or if the ridges and valleys of the wrinkles are individually extended obliquely with respect to the longitudinal and widthwise directions, on the other hand, the hydrophobic sheet being subjected to the elastic shrinking force is rounded or irregularly folded on the liquid receiving side of the absorbent article being worn. Then, the contact between the leakage preventing side walls and the wearer""s skin becomes unstable to form a clearance easily between the leakage preventing side walls and the skin. In this case, the sideway leakage cannot be completely prevented.
The invention has an object to provide an absorbent article which is enabled to curve the leakage preventing side walls easily in the widthwise direction to form a three-dimensional stereoscopic shape according to the shape of the skin of a wearer, by forming regions having a high bending rigidity in the widthwise direction, in advance in the leakage preventing side walls to be subjected to a shrinking force by elastic members and by making a rigidity difference in the widthwise direction.
According to an aspect of the invention, there is provided an absorbent article comprising: a main body including a support sheet, a liquid absorbing layer laid on the support sheet, and a liquid-permeable sheet provided on a liquid receiving side of the main body and covering the liquid absorbing layer; and leakage preventing side walls provided on two sides of the main body lying opposite one another in the widthwise direction and extending in the longitudinal direction, to have root ends jointed to the surface of the liquid receiving side and to have free ends positioned apart from the surface of the liquid receiving side, wherein each leakage preventing side wall includes: a nonwoven fabric comprising thermoplastic fibers; and an elastic member for exhibiting an elastic shrinking force in the longitudinal direction, wherein the nonwoven fabric is provided with: at least two rigid regions having corrugations, ridges and valleys of which are individually extended in a direction from the root end to the free end of the leakage preventing side wall and are repeated regularly in the longitudinal direction; and a rigid boundary portion in which the corrugations are discontinuous and which is extended in the longitudinal direction midway between the root end and the free end of the leakage preventing side wall.
In the invention, the nonwoven fabric making the leakage preventing side wall contains the thermoplastic fibers and is pressure/heat-shaped to form the regular corrugations. The ridges and valleys of the corrugations are individually extended in the widthwise direction on the leakage preventing side wall so that the rigid regions having the corrugations are higher in the widthwise bending rigidity. Therefore, the rigid regions are not extremely bent by an external force but can keep the extended state in the widthwise direction. Since the rigid boundary portion is formed midway between the root end and the free end, however, the leakage preventing side wall can be easily bent and deformed in the widthwise direction across the rigid boundary portion. Therefore, the leakage preventing side walls can be easily curved in the widthwise direction according to the curved shape of the skin of the wearer so that they can take the three-dimensional stereoscopic shapes easily. As a result, the leakage preventing side walls can come into close contact with the skin to prevent the sideway leakage effectively.
In the invention, since the leakage preventing side walls are made of the nonwoven fabric, they are sufficiently soft. If the corrugations are given a pitch as fine as 0.3 to 1.5 mm or more preferably about 0.5 to 1.0 mm, moreover, the leakage preventing side walls come into soft abutment against the skin so that the wearer hardly feels the sense of discomfort.
For example, midway between the root end and the free end of the leakage preventing side wall, there is formed a band-shaped region in which the nonwoven fabric is not corrugated or is corrugated lower than the corrugations and which is extended in the longitudinal direction, and a boundary line between the corrugations and the band-shaped region is the rigid boundary portion.
The leakage preventing side wall may have the elastic member attached to the free end but not to the vicinity of the rigid boundary portion.
In an alternative, the leakage preventing side wall may have the elastic member attached to the vicinity of the rigid boundary portion but not to the free end.
In another alternative, the leakage preventing side wall may have two elastic members attached to the free end and the vicinity of the rigid boundary portion, respectively. In this case, it is preferred that the elastic member at the free end has a higher elastic shrinking force than that of the elastic member in the vicinity of the rigid boundary portion.
The leakage preventing side wall may be made to have at least two sheet portions either by folding a single nonwoven fabric, as extending from the root end, back at the free end to the root end, or by jointing a plurality of nonwoven fabrics, as individually extending from the root end, to one another in the longitudinal direction at the free end or another region, and the rigid regions and the rigid boundary portion may be formed in the individual sheet portions at the same positions of the leakage preventing side wall.
Since the leakage preventing side wall is made of the two sheet portions of the nonwoven fabric, its leakage preventing effect as well as its rigidity in the rigid regions can be enhanced, and the leakage preventing side wall can be softly deformed across the rigid boundary portion.